JP5396429B2 - Gas concentration detection sensor - Google Patents

Description

  The present invention relates to a gas concentration detection sensor.

  2. Description of the Related Art Conventionally, a gas concentration detection sensor that detects a predetermined gas concentration such as NOx or oxygen in a measurement gas such as an automobile exhaust gas is known. In this gas concentration detection sensor, for example, water generated at the start of the engine may adhere to the sensor element, whereby the temperature of the sensor element may decrease and cracks may occur. Therefore, it has been proposed to prevent this by attaching a protective cover that covers the sensor element. For example, Patent Document 1 describes a gas sensor in which a protective cover having a double structure is provided on the outer periphery of the tip of a sensor element.

Japanese Unexamined Patent Publication No. 2000-304719 (FIG. 11)

  However, the protective cover has a hole for introducing the gas to be measured into the sensor element, and water may enter through the hole and adhere to the sensor element. In addition, in order to further suppress the adhesion of water, it is conceivable to increase the protective cover double or triple, and to complicate the flow path of the gas to be measured inside the protective cover. The time until the sensor element is reached increases, and the gas concentration detection responsiveness decreases. Therefore, a protective cover that can improve both the suppression of water adhesion to the sensor element and the response of gas concentration detection is desired.

  The present invention has been made to solve such problems, and has as its main object to provide a gas concentration detection sensor that improves the response of gas concentration detection while suppressing the adhesion of water to the sensor element. To do.

  The gas concentration detection sensor of the present invention employs the following means in order to achieve the main object described above.

The gas concentration detection sensor of the present invention is
A sensor element capable of detecting a predetermined gas concentration of the gas to be measured;
A bottomed cylindrical inner protective cover covering the tip of the sensor element;
An outer protective cover having a larger diameter than the inner protective cover and having a side surface and a bottom surface;
A plurality of outer gas holes opened in a boundary portion between a side surface and a bottom surface of the outer protective cover;
An inner gas hole that allows the flow of the gas to be measured inside and outside the inner protective cover, and is located on the rear end side of the sensor element with respect to the outer gas hole;
With
The angle formed by the external opening surface of the outer gas hole and the bottom surface of the outer protective cover is 10 ° to 80 °.

In this gas concentration detection sensor, the outer gas hole is opened at the boundary between the side surface and the bottom surface of the outer protective cover. The angle formed between the external opening surface of the outer gas hole and the bottom surface of the outer protective cover is 10 ° to 80 °. Therefore, compared to the case where the hole is located on the side surface or the angle between the external opening surface of the outer gas hole and the bottom surface of the outer protective cover is other than 10 to 80 °, the water that has entered the outer protective cover Easily escape from the hole to the outside. Thereby, it can suppress that water enters the inside protective cover and adheres to the sensor element. Further, the gas to be measured that enters the outer protective cover from the outer gas hole flows in the direction toward the rear end of the sensor element through the outer gas hole. Therefore, compared with the case where the outer gas hole is opened on the side surface of the outer protective cover or the angle formed by the external opening surface of the outer gas hole and the bottom surface of the outer protective cover is other than 10 to 80 °, the outer gas hole The gas to be measured easily enters the inner gas hole. As a result, the time during which the gas in the protective cover is replaced by the gas to be measured is shortened, and the responsiveness of the gas concentration detection sensor is improved. As described above, it is possible to improve the gas concentration detection responsiveness while suppressing the adhesion of water to the sensor element. The total area of the outer gas holes may be 6 to 13 mm ² .

  In the gas concentration detection sensor of the present invention, the outer protective cover connects the cylindrical barrel, the bottomed cylindrical tip having a smaller diameter than the barrel, and the barrel and the tip. And a plurality of the outer gas holes opened at a first corner that is a boundary portion between a side surface of the body portion of the outer protective cover and a bottom surface of the step portion of the outer protective cover. And a plurality of second outer gas holes opened at a second corner that is a boundary portion between the side surface and the bottom surface of the front end portion of the outer protective cover. The sensor element is located on the rear end side of the sensor element with respect to the first outer gas hole, and is surrounded by the body part and the step part of the outer protective cover and the inner protective cover, and is protected by the inner gas hole. A first gas chamber communicating with the inside of the cover; and a tip portion of the outer protective cover The flow of the gas to be measured between the second gas chamber surrounded by the inner protective cover and not directly communicating with the first gas chamber, and between the second gas chamber and the inner protective cover It is good also as what was provided with the gas passage hole which accept | permits. Also in this case, since water that has entered the outer protective cover easily escapes from the first outer gas hole and the second outer gas hole, it is possible to suppress water from entering the inner protective cover and adhering to the sensor element. Further, the gas to be measured that enters the first gas chamber from the first outer gas hole flows in the direction toward the rear end of the sensor element through the first outer gas hole. The inner gas hole is located closer to the rear end side of the sensor element than the first outer gas hole. As a result, the time during which the gas in the protective cover is replaced with the gas to be measured is shortened, and the responsiveness of the gas concentration detection sensor is improved.

  In the gas concentration detection sensor including the first outer gas hole and the second outer gas hole described above, the plurality of second outer gas holes have a total area of the opening part of the first outer gas hole. It may be larger. When the total area of the second outer gas holes is larger than the total area of the first outer gas holes, the second outer gas is more than the first outer gas holes in a transient state such as when the flow rate of the gas to be measured increases rapidly. More gas to be measured enters from the hole. As a result, in a transient state, pressure is generated from the second gas chamber into the inner protective cover and from the inner protective cover into the first gas chamber. By this pressure, the water in the first gas chamber is pushed out from the first outer gas hole. Thereby, adhesion of water to the sensor element can be further suppressed.

  Further, in a state other than the transient state, the tip portion of the outer protective cover has a bottomed cylindrical shape, so that the gas to be measured in the second gas chamber is second due to the flow of the gas to be measured along the bottom surface of the tip portion. It is sucked out from the outer gas hole. And since the total area of a 2nd outer side gas hole is larger than the total area of a 1st outer side gas hole, the force which sucks out this to-be-measured gas becomes large. As a result, the gas to be measured that has entered the first gas chamber from the first outer gas hole quickly escapes to the outside through the inner protective cover and the second gas chamber, and the responsiveness of the gas concentration detection sensor is improved. .

  In this case, the gas passage hole may be opened at a position other than the region on the extension of the second outer gas hole. Thereby, even if water enters from the second outer gas hole in the transient state, the water hardly reaches the inner protective cover. Thereby, adhesion of water to the sensor element can be further suppressed. Note that the region on the extension of the second outer gas hole refers to the light hitting the inner protective cover when light having virtually directivity is irradiated from the direction along the central axis of the second outer gas hole. Refers to an area.

  In the gas concentration detection sensor in which the total area of the openings of the second outer gas holes is larger than the total area of the openings of the first outer gas holes, the plurality of first outer gas holes all have an area of the opening. The plurality of second outer gas holes have the same opening area, and the plurality of second outer gas holes have an opening area per one of the first outer gas holes. It is good also as more than the area of the opening part per one.

  In the gas concentration detection sensor including the first outer gas hole and the second outer gas hole described above, the plurality of first outer gas holes may be three or more holes positioned at equal intervals, and the plurality of second gas holes. The outer gas holes may be three or more holes located at equal intervals. In this way, the first outer gas hole and the second outer gas hole facing the upstream side of the gas to be measured always exist regardless of the direction of the gas to be measured flowing from any direction on the outer peripheral surface of the outer protective cover. There will be a first outer gas hole and a second outer gas hole facing downstream of the measurement gas. Therefore, regardless of the direction in which the gas concentration detection sensor is installed, the gas to be measured can be reliably taken into the outer protective cover and the inner protective cover, and the gas concentration can be detected by the sensor element.

  In the gas concentration detection sensor including the first outer gas hole and the second outer gas hole described above, the gas passage hole is opened at a boundary portion between the side surface and the bottom surface of the inner protective cover, and the outside of the gas passage hole. An angle formed by the opening surface and the bottom surface of the inner protective cover may be 10 ° to 80 °. Accordingly, the gas to be measured that enters the second gas chamber from the inside of the inner protective cover flows toward the second outer gas hole by the gas passage hole. Therefore, when the gas passage hole is opened on the side surface or the bottom surface of the inner protective cover or when the angle formed by the external opening surface of the gas passage hole and the bottom surface of the inner protective cover is other than 10 ° to 80 °, The measurement gas that enters the second gas chamber from the inside of the inner protective cover easily reaches the second outer gas hole. Thereby, the time until the gas to be measured reaches the outside through the second gas chamber is shortened, and the responsiveness of the gas concentration detection sensor is improved.

4 is a schematic explanatory diagram of a state in which a gas concentration detection sensor 100 is attached to a pipe 200. FIG. 2 is a longitudinal sectional view illustrating a configuration of a gas concentration detection sensor 100. FIG. It is AA sectional drawing of FIG. Partial sectional view in which the periphery of the first outer gas hole 144a is enlarged It is the fragmentary sectional view which expanded the 2nd outer side gas hole 146a and gas passage hole 138a periphery. It is the fragmentary sectional view which expanded the 1st outside gas hole 144a circumference which changed the angle made. FIG. 6 is a longitudinal sectional view illustrating the configuration of another gas concentration detection sensor 300. FIG. 6 is a longitudinal sectional view illustrating the configuration of another gas concentration detection sensor 400. FIG. 6 is a longitudinal sectional view illustrating a configuration of another gas concentration detection sensor 500. FIG. 6 is a longitudinal sectional view showing the configuration of another gas concentration detection sensor 600. It is the fragmentary sectional view which expanded the circumference of gas passage hole 238a of a modification. It is the fragmentary sectional view which expanded the circumference of gas passage hole 239a of a modification. It is the fragmentary sectional view which expanded the circumference of gas passage hole 240a of a modification. It is explanatory drawing which shows the position of the gas passage hole 241a of a modification. It is explanatory drawing of the relationship between angle | corner (theta), length L, and length L2. It is explanatory drawing of angle (theta), length L, and length L2 which Example 6 and Comparative Example 1 make. It is explanatory drawing of angle (theta), length L, and length L2 which Example 7 and Comparative Example 2 make. It is a longitudinal cross-sectional view showing the structure of the gas concentration detection sensor 700 of Comparative Examples 3-5. 10 is a longitudinal sectional view illustrating a configuration of a gas concentration detection sensor 800 of Comparative Example 6. FIG. It is a top view (top view) of the intermediate protective cover 840. 10 is a longitudinal sectional view illustrating a configuration of a gas concentration detection sensor 900 of Comparative Example 7. FIG. It is explanatory drawing of the broken water amount measuring apparatus 950. FIG. It is the graph which plotted the response time of the density | concentration detection sensor of Examples 1-8 and Comparative Examples 1-7, and moisture. It is explanatory drawing which shows the mode of a vibration test. It is a graph which shows the result of the vibration test of Example 2, Comparative Examples 4 and 7. FIG. It is a graph which shows the result of the drain test of Example 8, and Comparative Examples 4 and 7. It is explanatory drawing of the state which inclined the gas concentration detection sensor of Example 8 45 degrees.

  Next, modes for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a schematic explanatory view of a state in which the gas concentration detection sensor 100 is attached to the pipe 200, FIG. 2 is a longitudinal sectional view showing the configuration of the gas concentration detection sensor 100, and FIG.

As shown in FIG. 1, the gas concentration detection sensor 100 is attached in a pipe 200 that is an exhaust path from the vehicle engine, and NOx and O ₂ contained in the exhaust gas as the measurement gas discharged from the engine. The concentration of at least one of the gas components such as is detected.

  As shown in FIG. 2, the gas concentration detection sensor 100 includes a sensor element 110 having a function of detecting the concentration of a gas component in the gas to be measured, and a protective cover 120 that protects the sensor element 110.

The sensor element 110 is an elongated plate-like element, and includes an oxygen ion conductive solid electrolyte layer such as zirconia (ZrO ₂ ). The sensor element 110 includes therein a heater that plays a role of temperature adjustment that heats and keeps the sensor element 110 warm. The principle of detecting the structure of the sensor element 110 and the concentration of the gas component is known, and is described in, for example, Japanese Patent Application Laid-Open No. 2008-164411.

  The protective cover 120 is disposed so as to surround the sensor element 110. The protective cover 120 includes an inner protective cover 130 that covers the tip of the sensor element 110 and an outer protective cover 140 that covers the inner protective cover 130. A first gas chamber 122 and a second gas chamber 126 are formed as a space surrounded by the inner protective cover 130 and the outer protective cover 140, and a sensor element chamber 124 is formed as a space surrounded by the inner protective cover 130. ing.

  The inner protective cover 130 is a member made of metal (for example, stainless steel), a cylindrical large-diameter portion 132, a cylindrical first body portion 134 having a diameter smaller than the large-diameter portion 132, and a cylindrical first member. A second body 136 having a diameter smaller than that of the first body 134 and a tip 138 having a bottomed cylindrical shape and a diameter smaller than that of the second body 136 are provided. The inner protective cover 130 includes a stepped portion 133 that connects the large-diameter portion 132 and the first body portion 134, a stepped portion 135 that connects the first body portion 134 and the second body portion 136, and a second body portion. A step portion 137 connecting the portion 136 and the tip portion 138 is provided. The large-diameter portion 132, the first body portion 134, the second body portion 136, and the tip portion 138 have the same central axis. The inner diameter surface of the large-diameter portion 132 is in contact with the metallic metal shell 102, so that the inner protective cover 130 is fixed to the metal shell 102. The first body portion 134 and the second body portion 136 are located so as to cover the side surface of the sensor element 110. The first body portion 134 has an inner gas hole 134a communicating with the first gas chamber 122 and the sensor element chamber 124, and a plate shape that regulates the flow of the gas to be measured flowing into the sensor element chamber 124 through the inner gas hole 134a. 6 guide portions 134b are formed at equal intervals, respectively (see FIG. 3). The inner gas holes 134a and the guide portions 134b are in one-to-one correspondence, and the guide portions 134b are formed so as to be positioned between the corresponding inner gas holes 134a and the sensor element 110. The plurality of guide portions 134b are formed to be rotationally symmetric (six-fold symmetric). Six gas passage holes 138 a communicating with the sensor element chamber 124 and the second gas chamber 126 are formed on the side surface of the distal end portion 138 at equal intervals. The gas passage hole 138a is formed such that a cross section perpendicular to the central axis of the gas passage hole 138a is a perfect circle.

  The outer protective cover 140 is a member made of metal (for example, stainless steel), and has a cylindrical large-diameter portion 142 and a cylindrical trunk portion that is connected to the large-diameter portion 142 and has a smaller diameter than the large-diameter portion 142. 144 and a tip portion 146 having a bottomed cylindrical shape and a diameter smaller than that of the body portion 144. Further, the outer protective cover 140 has a stepped portion 145 that connects the body portion 144 and the distal end portion 146. The central axes of the large diameter portion 142, the body portion 144, and the tip portion 146 are all the same as the central axis of the inner protective cover 130. The large-diameter portion 142 is in contact with the metal shell 102 and the large-diameter portion 132 on the inner peripheral surface, whereby the outer protective cover 140 is fixed to the metal shell 102. The body portion 144 is positioned so as to cover the outer peripheral surfaces of the first body portion 134 and the second body portion 136, and a first outer gas hole 144 a communicating with the outside of the outer protective cover 140 and the first gas chamber 122 is formed. Six places are formed at equal intervals. The first outer gas hole 144 a is a hole that is formed in a circular shape, and is located at a first corner portion 144 b that is a boundary portion between the side surface of the body portion 144 and the bottom surface of the stepped portion 145. Further, the first outer gas hole 144a has an angle of 45 ° between the outer opening surface of the first outer gas hole 144a and the bottom surface of the stepped portion 145, and the inner peripheral surface and the outer opening of the first outer gas hole 144a. The angle formed with the surface is 90 °. Here, the angle formed between the inner peripheral surface and the outer opening surface is 90 °, but the embodiment is not particularly limited to this. For example, the angle formed is other than 90 °. However, the effect of the present invention is achieved. FIG. 4 shows an enlarged partial cross-sectional view around the first outer gas hole 144a of FIG. As shown in FIG. 4, the angle formed by the external opening surface (dashed line a) of the first outer gas hole 144a and the bottom surface (dashed line b) of the stepped portion 145 is 45 °. Further, the angle formed by the inner peripheral surface 144c of the first outer gas hole 144a and the outer opening surface (dashed line a) of the first outer gas hole 144a is 90 °. The distal end portion 146 is positioned so as to cover the distal end portion 138, and the inner peripheral surface is in contact with the outer peripheral surface of the second body portion 136. Further, six second outer gas holes 146a communicating with the outer side of the outer protective cover 140 and the second gas chamber 126 are formed at equal intervals in the second corner portion 146b which is a boundary portion between the side surface and the bottom surface of the tip portion 146. Is formed. The second outer gas hole 146a is a hole formed in a circular shape, and, like the first outer gas hole 144a, the angle formed by the external opening surface of the second outer gas hole 146a and the bottom surface of the tip portion 146 is 45. And the angle formed by the inner peripheral surface of the second outer gas hole 146a and the outer opening surface is 90 °. The positional relationship between the second outer gas hole 146a and the gas passage hole 138a is determined so that the gas passage hole 138a is located at a position other than the region on the extension of the second outer gas hole 146a. FIG. 5 shows an enlarged partial cross-sectional view of the periphery of the second outer gas hole 146a and the gas passage hole 138a in FIG. As shown in FIG. 5, light having virtually directivity is irradiated from a direction along the central axis of the second outer gas hole 146a (an angle formed by the central axis direction of the outer protective cover 140 is 45 °). Then, a region 146c where the light strikes appears on the bottom surface of the front end portion 138 of the inner protective cover 130. This region 146c is referred to as a region on the extension of the second outer gas hole 146a. The gas passage hole 138a is located outside this region 146c. Note that the areas of the openings of the six first outer gas holes 144a are the same, and the areas of the openings of the six second outer gas holes 146a are the same. Moreover, the area of the opening part per 2nd outer gas hole 146a is larger than the area of the opening part per 1st outer gas hole. Therefore, since the first outer gas holes 144a and the second outer gas holes 146a are the same number (six locations), the total area of the second outer gas holes 146a (the area of one hole × the number of holes) is the first. It is larger than the total area of one outer gas hole 144a. The first outer gas hole 144a and the second outer gas hole 146a are formed so that a cross section perpendicular to the central axis thereof is a perfect circle. Although not particularly limited, in the present embodiment, the diameter of the first outer gas hole 144a is a value in the range of, for example, 0.8 to 1.2 mm, and the diameter of the second outer gas hole 146a is, for example, 0. A value in the range of .8 to 1.2 mm.

  The first gas chamber 122 is a space surrounded by the step portions 133 and 135, the first body portion 134, the second body portion 136, the large diameter portion 142, the body portion 144, and the step portion 145. The sensor element chamber 124 is a space surrounded by the inner protective cover 130. The second gas chamber 126 is a space surrounded by the step portion 137 and the tip portions 138 and 146. Note that the first gas chamber 122 and the second gas chamber 126 are not in direct communication with each other because the inner peripheral surface of the distal end portion 146 is in contact with the outer peripheral surface of the second body portion 136.

  Next, the flow of the gas to be measured when the gas concentration detection sensor 100 thus configured detects the concentration of the gas component will be described. First, the flow of the gas to be measured in a transient state such as when the flow rate of the gas to be measured flowing in the pipe 200 increases rapidly will be described. In this case, the gas to be measured flowing in the pipe 200 tends to enter the outer protective cover 140 from the first outer gas hole 144a and the second outer gas hole 146a. At this time, since the total area of the opening of the second outer gas hole 146a is larger than the total area of the opening of the first outer gas hole 144a, the object entering from the second outer gas hole 146a rather than the first outer gas hole 144a. The measurement gas increases. Thus, in a transient state, pressure is generated from the second gas chamber 126 through the gas passage hole 138a into the sensor element chamber 124 and from the sensor element chamber 124 through the inner gas hole 134a toward the first gas chamber 122. To do. Due to this pressure, the water in the first gas chamber 122 is pushed out of the outer protective cover 140 from the first outer gas hole 144a, so that it is difficult for the water to reach the sensor element chamber 124 from the first gas chamber 122. Further, since the gas passage hole 138a is opened at a position other than on the extension of the second outer gas hole 146a, even if water enters from the second outer gas hole 146a in the transient state, the water remains in the sensor element chamber 124. It is hard to reach inside. As a result, the adhesion of water to the sensor element 110 is further suppressed.

  Next, the flow of the gas to be measured in a state other than the transient state will be described. In this case, since the tip portion 146 of the outer protective cover 140 has a bottomed cylindrical shape, the gas to be measured in the second gas chamber 126 is caused to flow from the second outer side by the flow of the gas to be measured along the bottom surface of the tip portion 146. It is sucked out from the gas hole 146a and escapes. As a result, in a state other than the transient state, the gas to be measured enters the first gas chamber 122 through the first outer gas hole 144 a and passes through the sensor element chamber 124 and the second gas chamber 126 from the first gas chamber 122. 2 Outflow from the outer gas hole 146a. At this time, since the total area of the second outer gas hole 146a is larger than the total area of the first outer gas hole 144a, the force to suck out the measurement gas from the second outer gas hole 146a is increased. Further, the first outer gas hole 144a is formed in the first corner 144b, and the angle formed by the external opening surface of the first outer gas hole 144a and the bottom surface of the stepped portion 145 is 45 °. Thereby, the gas to be measured that enters the first gas chamber 122 from the first outer gas hole 144a flows in the rear end direction (upward direction in FIG. 2) of the sensor element 110 through the first outer gas hole 144a. As a result, as compared with the case where the first outer gas hole 144a is opened in the side surface of the outer protective cover 140, the time during which the gas in the protective cover 120 is replaced by the measured gas is shortened. That is, the responsiveness of the gas concentration detection sensor 100 is improved.

  The first outer gas hole 144a is formed in the first corner portion 144b, and the angle formed by the external opening surface of the first outer gas hole 144a and the bottom surface of the step portion 145 is 45 °. The second outer gas hole 146a is formed in the second corner portion 146b. The angle formed by the external opening surface of the second outer gas hole 146a and the bottom surface of the tip portion 146 is 45 ° and the second outer gas hole 146a. The angle formed by the inner peripheral surface and the outer opening surface is 90 °. Therefore, compared with the case where the first outer gas hole 144a and the second outer gas hole 146a are located on the side surface of the outer protective cover 140, the water that has entered the outer protective cover 140 is more water. It is easy to escape from the gas hole 146a to the outside. This also can prevent water from entering the sensor element chamber 124 and adhering to the sensor element 110.

  Furthermore, since the first outer gas hole 144a and the second outer gas hole 146a are six holes positioned at equal intervals, the gas to be measured flows from any direction on the outer peripheral surface of the outer protective cover 140. The first outer gas hole 144a and the second outer gas hole 146a that always face the upstream side of the gas to be measured always exist, and the first outer gas hole 144a and the second outer gas hole 146a that always face the downstream side of the gas to be measured always exist. Will do. Therefore, regardless of the direction in which the gas concentration detection sensor 100 is installed in the pipe 200, the gas to be measured is reliably taken into the outer protective cover 140 and the inner protective cover 130, and the concentration of the gas component is detected by the sensor element 110. be able to.

  According to the present embodiment described in detail above, the first outer gas hole 144a and the second outer gas hole 146a are opened at the positions and angles described above, whereby water adhesion to the sensor element 110 can be suppressed. Further, since the first outer gas hole 144a is opened at the position and angle described above, the responsiveness of the gas concentration detection sensor 100 is improved. Furthermore, since the total area of the openings of the second outer gas holes 146a is larger than the total area of the openings of the first outer gas holes 144a, water adhesion to the sensor element 110 can be further suppressed, and the gas concentration detection sensor 100 can be suppressed. Responsiveness is improved. Furthermore, since the first outer gas hole 144a and the second outer gas hole 146a are six holes positioned at equal intervals, the gas to be measured is surely taken into the outer protective cover 140 and the inner protective cover 130, and the sensor element. 110 can detect the concentration of the gas component.

  Note that the present invention is not limited to the above-described embodiments, and can be realized in various forms as long as they belong to the technical scope of the present invention.

  For example, in the above-described embodiment, the first outer gas hole 144a and the second outer gas hole 146a are both six holes, but the present invention is not limited to this. For example, the first outer gas holes 144a may be three or more holes positioned at equal intervals, and the second outer gas holes 146a may be three or more holes positioned at equal intervals. In this way, as in the above-described embodiment, the first outer gas hole 144a and the second outer gas hole 146a always face the upstream side of the gas to be measured, and the first outer side always faces the downstream side of the gas to be measured. Since the gas hole 144a and the second outer gas hole 146a exist, the gas to be measured can be reliably taken into the outer protective cover 140 and the inner protective cover 130. Further, the first outer gas hole 144a and the second outer gas hole 146a may both be two holes. In this case, the first outer gas hole 144a and the second outer gas hole 146a facing the upstream of the gas to be measured exist, and the first outer gas hole 144a and the second outer gas hole 146a facing the downstream of the gas to be measured. If the gas concentration detection sensor 100 is arranged in the pipe 200 so that there is, the effect of reliably taking the gas under measurement into the outer protective cover 140 and the inner protective cover 130 can be obtained. The first outer gas hole 144a and the second outer gas hole 146a may not be located at equal intervals.

  In the embodiment described above, the areas of the openings of the six first outer gas holes 144a are all the same, and the areas of the openings of the six second outer gas holes 146a are the same. However, the present invention is not limited to this, and a hole having a different area of the opening may be provided. Even in this case, if the total area of the opening of the second outer gas hole 146a is larger than the total area of the opening of the first outer gas hole 144a, the water in the first gas chamber 122 in the transient state is discharged. Sufficient pressure is obtained to push out the first outer gas hole 144a to the outside of the outer protective cover 140 and to suck out the measurement gas from the second outer gas hole 146a in a state other than the transient state. Even if the total area of the openings of the second outer gas holes 146a is equal to or less than the total area of the openings of the first outer gas holes 144a, the first outer gas holes 144a are opened in the first corners 144b. Thus, the effect of suppressing the adhesion of water to the sensor element 110 and the response of the gas concentration detection sensor 100 due to the second outer gas hole being formed in the second corner 146b can be obtained.

  In the embodiment described above, the angle formed by the external opening surface of the first outer gas hole 144a and the bottom surface of the stepped portion 145 is 45 °, but is not limited thereto. For example, the angle formed may be a value in the range of 10 ° to 80 °. Even in this case, if the first outer gas hole 144a is positioned at the first corner 144b, the water easily escapes from the first outer gas hole 144a to the outside, and the effect of suppressing the adhesion of water to the sensor element 110 is suppressed. Is obtained. “The first gas hole 144a is located at the first corner 144b” means the first corner 144b (in other words, the rising portion between the side surface of the body portion 144 and the bottom surface of the step portion 145). This means that the first gas hole 144a includes (overlaps) at least a part of the region. When the angle formed is a value other than 45 °, for example, as shown in FIG. 6A, the angle of the central axis of the first outer gas hole 144a (the angle at which the first outer gas hole 144a is opened) is set as shown in FIG. The first outer gas hole 144a may be formed by setting the same 45 ° as that of the first outer gas hole 144a and shifting the position of opening the hole. For example, as shown in FIG. 6B, the first outer gas hole 144a may be formed by setting the angle of the central axis of the first outer gas hole 144a to an angle different from that in FIG. In FIGS. 6A and 6B, the portion surrounded by the broken line is the first corner 144b, and the alternate long and short dash line is the central axis of the first outer gas hole 144a. In FIGS. 6A and 6B, the angles formed by the external opening surface of the first outer gas hole 144a and the bottom surface of the stepped portion 145 are 80 ° and 50 °, respectively. 6A and 6B, the first outer gas hole 144a includes at least a part of the first corner 144b, and the first outer gas hole 144a includes the first gas hole 144a. Since the angle formed by the external opening surface of the step and the bottom surface of the stepped portion 145 is in the range of 10 ° to 80 °, the effect of suppressing the adhesion of water to the sensor element 110 is obtained. Further, similarly to the first outer gas hole 144a, the angle formed by the external opening surface of the second outer gas hole 146a and the bottom surface of the distal end portion 146 is 45 ° in the present embodiment. A value in the range of ° may be used. Even in this case, if the second outer gas hole 146a is located at the second corner portion 146b, water can easily escape from the second outer gas hole 146a to the outside, and the effect of suppressing the adhesion of water to the sensor element 110 is suppressed. Is obtained. “The second gas hole 146a is located at the second corner 146b” means at least a part of the second corner 146b (in other words, the rising portion between the side surface and the bottom surface of the tip 146). This means that the second gas hole 146a includes (overlaps) this area.

  Instead of the gas concentration detection sensor 100 of the embodiment described above, a gas concentration detection sensor 300 shown in FIG. 7 may be adopted. The gas concentration detection sensor 300 includes an inner protective cover 330 and an outer protective cover 340 as the protective cover 320. The inner protective cover 330 has the same structure as the inner protective cover 130 of FIG. 2 except that the shapes of the tip end portion 338 and the gas passage hole 338a are different from those of the tip end portion 138 and the gas passage hole 138a and that the step portion 137 is not provided. For this reason, constituent elements other than the tip 338 and the gas passage hole 338a are denoted by the same reference numerals, and detailed description thereof is omitted. Unlike the tip end portion 138, the tip end portion 338 has a shape in which a triangular frustum is inverted. Further, the gas passage hole 338 a is a circular hole located at the center point of the bottom surface of the tip end portion 338. Since the outer protective cover 340 has the same structure as that of the outer protective cover 140 in FIG. 2, the same reference numerals are given to the components, and detailed description thereof is omitted. Also in such a gas concentration detection sensor 300, the same effect as the above-described embodiment can be obtained.

  A gas concentration detection sensor 400 shown in FIG. 8 may be employed instead of the gas concentration detection sensor 100 of the above-described embodiment. The protective cover 420 of the gas concentration detection sensor 400 covers the first inner protective cover 430 that covers the tip of the sensor element 110, the second inner protective cover 440 that covers the first inner protective cover 430, and the second inner protective cover 440. It has a triple structure including an outer protective cover 450. The first inner protective cover 430 has a cylindrical large-diameter portion 432 and a bottomed cylindrical tip portion 434, the outer peripheral surface of which is in contact with the metal metallic shell 402. Twelve gas passage holes 434a are formed in the side surface of the tip portion 434, and one gas passage hole 434b is formed in the center of the bottom surface of the tip portion 434. The gas passage holes 434a are formed at equal intervals at positions shifted in two stages in the axial direction (vertical direction in FIG. 8) in a zigzag manner. The second inner protective cover 440 has an inner peripheral surface in contact with the metallic metal shell 402 and has a cylindrical large-diameter portion 442, a cylindrical trunk portion 444, and a bottomed cylindrical tip portion 446. Have. The large diameter portion 442 and the body portion 444 are connected via a step portion 443, and the body portion 444 and the tip portion 446 are also connected via a step. The stepped portion 443 has six inner gas holes 443a formed at equal intervals. One gas passage hole 446 a is formed at the center of the bottom surface of the distal end portion 446. The outer protective cover 450 has a cylindrical large-diameter portion 452 and a bottomed cylindrical tip portion 454 whose inner peripheral surface is in contact with the metallic metallic shell 402. Six circular outer gas holes 454a are formed at the boundary portion between the side surface and the bottom surface of the tip portion 454. The outer gas hole 454a is formed such that an angle θ1 formed by the outer opening surface of the outer gas hole 454a and the bottom surface of the tip portion 454 is 10 ° to 80 °. The front end 434 of the first inner protective cover 430 and the front end 446 of the second inner protective cover 440 are in contact with each other, and as a result, the first inner protective cover 430 and the second inner protective cover 440 are surrounded. The space is separated into an upper chamber 422 and a lower chamber 424. Also in such a gas concentration detection sensor 400, the following effects can be obtained. That is, since the water that has entered the outer protective cover 450 easily escapes from the outer gas hole 454a to the outside, the water enters the second inner protective cover 440 and the first inner protective cover 430 and adheres to the sensor element 110. Can be suppressed. In addition, the gas to be measured that enters the outer protective cover 450 from the outer gas hole 454a flows in the rear end direction (upward direction in FIG. 8) of the sensor element 110 through the outer gas hole 454a. Since the inner gas hole 443a is positioned closer to the rear end of the sensor element 110 than the outer gas hole 454a as shown in the figure, the gas to be measured that has entered from the outer gas hole 454a easily reaches the inner gas hole 443a. . As a result, the time during which the gas in the protective cover 420 is replaced with the gas to be measured is shortened, and the responsiveness of the gas concentration detection sensor is improved.

  Instead of the gas concentration detection sensor 100 of the embodiment described above, a gas concentration detection sensor 500 shown in FIG. 9 may be adopted. The protective cover 520 of the gas concentration detection sensor 500 has a double structure including an inner protective cover 530 that covers the tip of the sensor element 110 and an outer protective cover 540 that covers the inner protective cover 530. The inner protective cover 530 has a cylindrical large-diameter portion 532 and a bottomed cylindrical tip portion 534 having an inner peripheral surface in contact with the metal metal shell 502. The large diameter portion 532 and the tip portion 534 are connected via a step. Six inner gas holes 534a are formed at equal intervals on the side surface of the distal end portion 534. The outer protective cover 540 has a cylindrical large-diameter portion 542 and a bottomed cylindrical tip portion 544 that have an inner peripheral surface in contact with the metallic metal shell 502. Six gas passage holes 544a are formed at equal intervals on the side surface of the distal end portion 544. In addition, six circular outer gas holes 544b are formed at the boundary portion between the side surface and the bottom surface of the tip portion 544. The outer gas hole 544b has an angle θ2 formed between the outer opening surface of the outer gas hole 544b and the bottom surface of the tip portion 544 of 10 ° to 80 °, and the outer gas hole 544b has an inner peripheral surface and an outer opening surface. The formed angle is 90 °. Also in such a gas concentration detection sensor 500, the following effects can be obtained. That is, since water that has entered the outer protective cover 540 easily escapes from the outer gas hole 544b to the outside, it is possible to suppress water from entering the inner protective cover 530 and adhering to the sensor element 110. Further, the gas to be measured that enters the outer protective cover 540 from the outer gas hole 544b flows in the rear end direction (upward direction in FIG. 9) of the sensor element 110 through the outer gas hole 544b. Since the inner gas hole 534a is located closer to the rear end of the sensor element 110 than the outer gas hole 544b as shown in the figure, the gas to be measured that has entered from the outer gas hole 544b easily reaches the inner gas hole 534a. . As a result, the time during which the gas in the protective cover 520 is replaced with the gas to be measured is shortened, and the responsiveness of the gas concentration detection sensor is improved.

  Instead of the gas concentration detection sensor 100 of the embodiment described above, a gas concentration detection sensor 600 shown in FIG. 10 may be adopted. The protective cover 620 of the gas concentration detection sensor 600 has a double structure including an inner protective cover 630 that covers the tip of the sensor element 110 and an outer protective cover 640. The inner protective cover 630 has a cylindrical large-diameter portion 632 and a bottomed cylindrical tip portion 634, the inner peripheral surface of which is in contact with the metallic metal shell 602. The large diameter portion 632 and the tip portion 634 are connected via a step. The tip portion 634 contains an inner gas hole (not shown) that allows the flow of the gas to be measured inside and outside the inner protective cover 630 and the flow of the gas to be measured that flows into the inner protective cover 630 through the inner gas hole. Six plate-shaped guide portions 634b to be regulated are formed at equal intervals. The inner gas hole and guide part 634b are the same as the inner gas hole 134a and guide part 134b shown in FIGS. Further, six circular gas passage holes 634c are formed at the boundary portion between the side surface and the bottom surface of the tip portion 634. The gas passage hole 634c is formed such that an angle θ3 formed by the external opening surface of the gas passage hole 634c and the bottom surface of the tip portion 634 is 10 ° to 80 °. The outer protective cover 640 has a cylindrical large-diameter portion 642 whose inner peripheral surface is in contact with the metal metal shell 602 and a tip portion 644 having a side surface and a bottom surface. A hole is formed in the bottom surface of the distal end portion 644, and the distal end portion 634 of the inner protective cover 630 passes through the hole. In addition, the inner peripheral surface 644 b of the hole on the bottom surface of the distal end portion 644 is welded to the side surface of the distal end portion 634 of the inner protective cover 630. In addition, six circular outer gas holes 644a are formed at the boundary portion between the side surface and the bottom surface of the tip portion 644. The outer gas hole 644a is formed such that an angle θ4 formed by the outer opening surface of the outer gas hole 644a and the bottom surface of the tip end portion 644 is 10 ° to 80 °. Also in such a gas concentration detection sensor 600, the following effects can be obtained. That is, the water that has entered the outer protective cover 640 and the water that has entered the inner protective cover 630 can easily escape to the outside from the outer gas hole 644a and the gas passage hole 634c. Adhesion to the element 110 can be suppressed. Further, the gas to be measured that enters the outer protective cover 640 from the outer gas hole 644a flows in the rear end direction (upward direction in FIG. 10) of the sensor element 110 through the outer gas hole 644a. As can be seen from the positional relationship between the guide portion 634b and the outer gas hole 644a, the inner gas hole is located closer to the rear end of the sensor element 110 than the outer gas hole 644a. For this reason, the gas to be measured that has entered from the outer gas hole 644a easily reaches the inner gas hole. Thereby, the time during which the gas in the protective cover 620 is replaced with the gas to be measured is shortened, and the responsiveness of the gas concentration detection sensor is improved.

  In the above-described embodiment, as shown in FIGS. 2 and 5, the gas passage hole 138 a is located on the side surface of the front end portion 138 of the inner protective cover 130. You may locate in the boundary part of a side surface and a bottom face. FIG. 11 shows an enlarged partial cross-sectional view of the periphery of the gas passage hole when the gas passage hole is located at the boundary portion between the side surface and the bottom surface of the inner protective cover. In FIG. 11, the same components as those in FIG. 5 are denoted by the same reference numerals, and detailed description thereof is omitted. As shown in the figure, the gas passage hole 238a of the modified example is different from the gas passage hole 138a of FIG. 5 in that the angle formed by the outer opening surface of the gas passage hole 238a and the bottom surface of the front end portion 138 of the inner protective cover 130 is 45. And the angle formed by the inner peripheral surface of the gas passage hole 238a and the outer opening surface is 90 °. The angle formed between the outer opening surface of the gas passage hole 238a and the bottom surface of the front end portion 138 of the inner protective cover 130 is not limited to 45 °, and may be a value in the range of 10 to 80 °. In this way, the gas to be measured that enters the second gas chamber 126 from the sensor element chamber 124 flows toward the second outer gas hole 146a through the gas passage hole 238a. Therefore, compared to the case where the gas passage hole is opened on the side surface or the bottom surface of the tip portion 138 and the angle between the external opening surface of the gas passage hole and the bottom surface of the tip portion 138 is other than 10 ° to 80 °, The gas to be measured that enters the second gas chamber 126 from the sensor element chamber 124 easily reaches the second outer gas hole 146a. Thereby, the time until the gas to be measured reaches the outside through the second gas chamber 126 is shortened, and the responsiveness of the gas concentration detection sensor is improved. Even if the gas passage hole 238a is positioned so as to overlap the region 146c, the effect of improving the responsiveness of the gas concentration detection sensor can be obtained.

  In the above-described embodiment, as shown in FIGS. 2 and 5, the gas passage hole 138 a is located in the middle of the side surface of the front end portion 138 of the inner protective cover 130. The passage hole may be provided at a position near the bottom surface of the side surface of the tip portion 138 or may be provided at a position near the step portion 137. FIG. 12 shows an enlarged partial cross-sectional view of the periphery of the gas passage hole when the gas passage hole is provided at a position near the bottom surface of the side surface of the tip portion 138. In FIG. 12, the same components as those in FIG. 5 are denoted by the same reference numerals, and detailed description thereof is omitted. As illustrated, the modified gas passage hole 239a is provided at a position as close as possible to the corner 138b of the tip 138. Further, the lowermost surface 239b of the gas passage hole 239a and the bottom surface 138c inside the tip portion 138 are located on the same plane.

In the above-described embodiment, as shown in FIGS. 2 and 5, the gas passage hole 138 a is located on the side surface of the front end portion 138 of the inner protective cover 130. It may be. FIG. 13 shows an enlarged partial cross-sectional view of the periphery of the gas passage hole when the gas passage hole is located on the bottom surface of the tip portion 138. In FIG. 13, the same components as those in FIG. 5 are denoted by the same reference numerals, and detailed description thereof is omitted. As shown in the figure, the modified gas passage hole 240 a is a circular hole located at the center of the bottom surface of the tip 138. Note that the gas passage hole may be provided at a position other than the center of the bottom surface of the tip end portion 138. For example, you may provide a gas passage hole in the bottom face of the front-end | tip part 138 in the position as close as possible to the corner | angular part of the front-end | tip part 138. In this case, when the distal end portion 138 is viewed from the central axis direction (vertical direction in FIG. 2), the position of the gas passage hole centered on the central axis of the distal end portion 138 and the extension of the second outer gas hole 146a. The gas passage hole may be positioned other than the region 146c by disposing the phase so as to be out of phase with the position of the region 146c. An explanatory view showing the position of the gas passage hole in this case is shown in FIG. FIG. 14A is a partial cross-sectional view around the tip 138, and FIG. 14B is a cross-sectional view taken along the line BB in FIG. 14A. In FIG. 14, the same components as those in FIG. 5 are denoted by the same reference numerals, and detailed description thereof is omitted. As shown in FIG. 14B, the gas passage holes 241a of the modified example are formed at six locations at equal intervals, and are formed at positions as close as possible to the corner portion 138b of the bottom surface of the tip portion 138. Therefore, as shown in FIG. 14B, the gas passage hole 241 a is positioned so as to be in contact with the inner peripheral surface of the side portion of the tip portion 138 when viewed from the central axis direction. The gas passage hole 241a is arranged such that the phase between the position of the gas passage hole 241a and the position of the region 146c is shifted when viewed from the center axis of the tip end portion 138 as the center point. Thereby, the gas passage hole 241a is positioned so as not to overlap the region 146c. Even when the gas passage hole 241a is formed in this way, the gas passage hole 241a is opened at a position other than the region 146c, so that it is difficult for water to reach the sensor element chamber 124 as in the present embodiment. Is obtained.

  In the embodiment described above, the gas passage hole 138a, the first outer gas hole 144a, and the second outer gas hole 146a are formed so that the cross section perpendicular to the central axis thereof is a perfect circle. It is not limited to this. For example, the cross section perpendicular to the central axis may be an ellipse or a polygon (for example, a rectangle).

[Examples 1-2]
A plurality of gas concentration detection sensors 100 shown in FIG. 2 were produced. Specifically, as the inner protective cover 130, the plate thickness is 0.3 mm, the axial length of the large-diameter portion 132 is 1.9 mm, the axial length of the first barrel portion 134 is 5.2 mm, and the second barrel portion. The axial length of 136 is 5.2 mm, the axial length of the tip portion 138 is 4.9 mm, the inner diameter of the large diameter portion 132 is 13.54 mm, the inner diameter of the first body portion 134 is 11.2 mm, and the second body A portion 136 having an inner diameter of 7.6 mm, a tip portion 138 having an inner diameter of 5.3 mm, and the size of the opening of the inner gas hole being 1.5 mm in length and 0.3 mm in width was used. Further, as the outer protective cover 140, the plate thickness is 0.4 mm, the axial length of the large diameter portion 142 is 5.6 mm, the axial length of the body portion 144 is 9.2 mm, and the axial length of the distal end portion 146 is. Is 9.6 mm, the inner diameter of the large-diameter portion 142 is 14.4 mm, the inner diameter of the body portion 144 is 13.8 mm, the inner diameter of the tip portion 146 is 7.9 mm, and the bending radii of the first corner portion 144b and the second corner portion 146b A material having an R of 1.0 mm was used. And what changed variously the internal diameter (phi) 1 of the 1st outer side gas hole 144a of the outer side protective cover 140 and the internal diameter (phi) 2 of the 2nd outer side gas hole 146a as shown in Examples 1-2 of Table 1 was produced. The “angle of the gas passage hole” in Table 1 means an angle formed by the external opening surface of the gas passage hole of the inner protective cover and the bottom surface of the front end portion of the inner protective cover. As can be seen from FIG. 2, in Examples 1 and 2, the angle of the gas passage hole is 90 °. In addition, the sensor element 110 of the gas concentration detection sensor 100 produced here detects the oxygen concentration.

[Examples 3 to 5]
Except that the number of holes and the inner diameters φ1 and φ2 of the first outer gas hole 144a and the second outer gas hole 146a are the values shown in Examples 3 to 5 in Table 1, the same ones as in Examples 1 and 2 are manufactured. did.

[Examples 6-7, Comparative Examples 1-2]
The angle formed between the outer opening surface of the first outer gas hole 144a and the bottom surface of the stepped portion 145 and the angle formed between the outer opening surface of the second outer gas hole 146a and the bottom surface of the tip end portion 146 are set to the same value θ. Except for the point that the value θ was changed as shown in Table 1, the same ones as in Example 1 were created and used as Examples 6-7 and Comparative Examples 1-2. As shown in FIG. 6 (a), the angle formed by shifting the position of opening the hole with the central axis angle of the first outer gas hole 144a set to 45 ° same as the first outer gas hole 144a of FIG. θ was changed. When the angle θ formed in this way is changed, the external opening of the first outer gas hole 144a extends from the central axis direction length L of the outer protective cover 140 of the outer opening surface of the first outer gas hole 144a and the outer peripheral surface of the trunk portion 144. The length L2 (see FIG. 15) to the portion of the surface closest to the central axis of the outer protective cover 140 changes. The length L in Example 1 (the angle θ = 45 °) was 0.71 mm. When the angle θ formed as in Example 6 and Comparative Example 1 is reduced to 10 ° and 5 °, the length L is reduced to 0.21 mm and 0.11 mm, and the length L2 is 1.20 mm. It became as large as 30 mm (FIGS. 15A and 15B). When the value of the angle θ formed as in Example 7 and Comparative Example 2 is increased to 80 ° and 85 °, the length L is increased to 1.20 mm and 1.30 mm, the length L2 is 0.22 mm, It was as small as 0.13 mm (FIGS. 17A and 17B). The relationship between the angle θ and the lengths L and L2 is the same in the second outer gas hole 146a. 16 and 17, in Examples 6 to 7 and Comparative Examples 1 and 2, the angle formed by the inner peripheral surface of the first outer gas hole 144a and the outer opening surface is different from that in FIG. It is a value other than °. The same applies to the second outer gas hole 146a.

[Example 8]
The front end portion 138 of the inner protective cover 130 includes the gas passage hole 238a shown in FIG. 11 instead of the gas passage hole 138a (specifically, the gas passage hole 238a is provided at the boundary between the side surface and the bottom surface of the front end portion 138). Except that the angle formed by the external opening surface of the gas passage hole 238a and the bottom surface of the tip portion 138 is 45 °), a device similar to that of the second embodiment is manufactured to be the eighth embodiment. . The gas passage holes 238a have an inner diameter of 1.0 mm and are formed at six equal intervals.

[Comparative Examples 3 to 5]
A plurality of gas concentration detection sensors 700 shown in FIG. 18 were produced. The gas concentration detection sensor 700 includes an inner protective cover 730 and an outer protective cover 740 as the protective cover 720. The inner protective cover 730 has the same structure as the inner protective cover 130 in FIG. 2 except that the shapes of the tip end portion 738 and the gas passage hole 738a are different from those of the tip end portion 138 and the gas passage hole 138a and that the step portion 137 is not provided. For this reason, constituent elements other than the distal end portion 738 and the gas passage hole 738a are denoted by the same reference numerals and detailed description thereof is omitted. Unlike the tip end portion 138, the tip end portion 738 has a shape in which the triangular frustum is inverted. The inner diameter of the portion connected to the body portion 136 is 7.4 mm, and the diameter of the bottom surface is 2.4 mm. The gas passage hole 738a is a circular hole located at the center point of the bottom surface of the tip end portion 738, and has an inner diameter of 1 mm. The angle formed between the external opening surface of the gas passage hole 738a and the bottom surface of the tip portion 738 is 0 °. Since the outer protective cover 740 has the same structure as the outer protective cover 140 of FIG. 2 except for the first outer gas hole 744a and the second outer gas hole 746a, the outer protective cover 740 has a structure other than the first outer gas hole 744a and the second outer gas hole 746a. Constituent elements are denoted by the same reference numerals, and detailed description thereof is omitted. The first outer gas hole 744 a is located on the side surface of the body portion 144, and the second outer gas hole 746 a is located on the side surface of the distal end portion 146. Then, the inner diameter φ1 of the first outer gas hole 744a of the outer protective cover 740 and the inner diameter φ2 of the second outer gas hole 746a were variously changed as shown in Comparative Examples 1 to 3 in Table 1. In addition, the 1st outer side gas hole 744a and the 2nd outer side gas hole 746a opened six places at equal intervals similarly to Examples 1-2.

[Comparative Example 6]
A gas concentration detection sensor 800 shown in FIG. 19 was produced. The protective cover 820 of the gas concentration detection sensor 800 includes a 0.3 mm thick inner protective cover 830 that covers the tip of the sensor element 110, a 0.3 mm thick intermediate protective cover 840 that covers the inner protective cover 830, and an intermediate protective cover. It has a triple structure including an outer protective cover 850 having a thickness of 0.4 mm that covers the cover 840. The inner protective cover 830 has a cylindrical large-diameter portion 832 whose outer peripheral surface is in contact with a metallic metal shell 802, has an axial length of 5.5 mm, and an inner diameter of 6.8 mm, and an axial length of 13 mm. And a bottomed cylindrical tip 834 having an inner diameter of 6.4 mm and an inner diameter of 6.4 mm. Twelve inner gas holes 834a with an inner diameter of 1.5 mm are formed on the side surface of the tip portion 834, and one gas passage hole 834b with an inner diameter of 5 mm is formed at the center of the bottom surface of the tip portion 834. Yes. The angle formed between the external opening surface of the gas passage hole 834b and the bottom surface of the tip portion 834 is 0 °. The inner gas holes 834a are formed at equal intervals at positions shifted in two stages in the axial direction (vertical direction in FIG. 19) in a zigzag manner. The intermediate protective cover 840 has a large-diameter portion 842 whose inner peripheral surface is in contact with a metallic metal shell 802, has an axial length of 1.8 mm and an inner diameter of 13.9 mm, and an axial length of 8.4 mm. And a cylindrical body portion 844 having an inner diameter of 9.1 mm and a bottomed cylindrical tip portion 846 having an axial length of 5.5 mm and an inner diameter of 6.9 mm. The large-diameter portion 842 and the body portion 844 are connected via a step portion 843, and the body portion 844 and the distal end portion 846 are also connected via a step. As shown in FIG. 20, the stepped portion 843 is formed with six arc-shaped first intermediate gas holes 843 a having a width of 1 mm and an angle of 40 ° with a circle having a diameter of 11.6 mm as the center line at equal intervals. . One second intermediate gas hole 846a having an inner diameter of 1.1 mm is formed at the center of the bottom surface of the distal end portion 846. The outer protective cover 850 has a cylindrical large-diameter portion 852 having an inner peripheral surface abutting against a metal metal shell 802, an axial length of 5.6 mm, and an inner diameter of 14.4 mm, and an axial length of 850 mm. And a bottomed cylindrical tip 854 having an inner diameter of 18.2 mm and an inner diameter of 13.8 mm. Six outer gas holes 854a having an inner diameter of 2 mm are formed on the side surface of the distal end portion 854. Note that the front end portion 834 of the inner protective cover 830 and the front end portion 846 of the intermediate protective cover 840 are in contact with each other. As a result, the space surrounded by the inner protective cover 830 and the intermediate protective cover 840 is the upper chamber 822. It is separated into a lower chamber 824.

[Comparative Example 7]
A gas concentration detection sensor 900 shown in FIG. 21 was produced. The protective cover 920 of the gas concentration detection sensor 900 includes an inner protective cover 930 having a thickness of 0.3 mm that covers the tip of the sensor element 110, and an outer protective cover 940 having a thickness of 0.4 mm that covers the inner protective cover 930. Has a double structure. The inner protective cover 930 has a cylindrical large-diameter portion 932 having an inner peripheral surface abutting against a metal metal shell 902, an axial length of 1.5 mm, and an inner diameter of 13.7 mm, and an axial length. It has a bottomed cylindrical tip 934 having a diameter of 12.4 mm and an inner diameter of 6.9 mm. The large diameter portion 932 and the tip portion 934 are connected via a step. Six inner gas holes 934a having an inner diameter of 1.5 mm are formed on the side surface of the distal end portion 934 at equal intervals. The outer protective cover 940 has a cylindrical large-diameter portion 942 having an inner circumferential surface that is in contact with the metal metal shell 902, an axial length of 5.5 mm, and an inner diameter of 14.4 mm, and an axial length of A bottomed cylindrical tip 944 having an inner diameter of 15.3 mm and an inner diameter of 13.8 mm. Six first outer gas holes 944a having an inner diameter of 2 mm are formed at equal intervals on the side surface of the tip portion 944. One second outer gas hole 944b having an inner diameter of 3.8 mm is formed at the center of the bottom surface of the tip end portion 944.

[Evaluation Test 1]
For the gas concentration detection sensors of Examples 1 to 8 and Comparative Examples 1 to 7, the following sensor output responsiveness and water sensitivity of the sensor elements were examined. The results are shown in Table 1 and FIG. The test method of the response of the sensor output and the wetness of the sensor element is as follows.

-Responsiveness of sensor output First, a gas concentration detection sensor was attached to the pipe 200 as shown in FIG. In this state, instead of engine exhaust gas, a reference gas controlled to a NO concentration of 70 ppm and lambda 1.05 by burner combustion was flowed as a measurement gas, and the sensor output was awaited. Thereafter, oxygen was introduced into the reference gas through the gas inlet, and a mixed gas having a NO concentration of 70 ppm and lambda 1.35 was allowed to flow until the sensor output was stabilized. Then, the sensor element 110 functions as an oxygen concentration cell, an electromotive force is generated, and the sensor output rises. Here, from the time when oxygen is introduced into the reference gas, the time t10 required for the sensor output to reach 10% of the maximum rise value and the time required for the sensor output to reach 90% of the maximum rise value. t90 was obtained, and the difference Δt (= t90−t10) was taken as the response time (unit: sec). The shorter the response time, the higher the response of the gas concentration detection sensor.

-Water resistance of sensor element The water resistance was calculated | required using the broken water amount measuring apparatus 950 shown in FIG. That is, as a broken water amount measuring device 950, two pipes 960 and 970 having a diameter of 28 mm are connected so as to have an angle of 150 °, and a blower 980 is connected to a position 300 mm from the joint via a switching valve 990. A gas concentration detection sensor 100 was prepared at a position of 400 mm from the joint toward the side opposite to the blower 980. And the air blower 980 was drive | operated on the predetermined drive condition in the state which stored the arbitrary amount of water in the joint part, and it ventilated from the air blower 980 to the pipe 960. The air at the joint portion was scattered toward the sensor 100 by this air blowing, and all the stored water was discharged out of the pipe 970. At that time, it was confirmed whether or not an abnormality was found in the output from the sensor element 110. For one gas concentration detection sensor, perform the same test 10 times with the same amount of water. If no abnormality is observed once, increase the amount of water by 10 cm ^{3 and} repeat the test 10 times. The test was repeated in the same manner while increasing the amount of water by 10 cm ³ until abnormality was observed. Then, the amount of water at the beginning of the test when an abnormality was observed even once was broken and the amount of water (unit: liter) was taken, and the reciprocal of this amount of broken water was taken as water coverage (unit: 1 / liter). The smaller the water coverage is, the more water adhesion to the sensor element 110 is suppressed. Note that the predetermined driving condition of the blower means that after the energization of the heater of the sensor element 110 is finished, the blower 980 connects the bypass valve 990 shown in FIG. The flow is made, the switching valve 990 is switched to the pipe 960, and the air is sent to the pipe 960 for 3 seconds.

  FIG. 23 is a graph in which the response time and the moisture content of each gas concentration detection sensor of Examples 1 to 8 and Comparative Examples 1 to 7 are plotted. As is clear from Table 1 and FIG. 23, each of Examples 1 to 8 has a shorter response time and a lower water repellency value than Comparative Examples 3 to 7. Further, in Examples 2, 4, and 5 in which the total area of the second outer gas hole 146a is larger than the total area of the first outer gas hole 144a, the total area of the second outer gas hole 146a and the first outer gas hole 146a Compared with Examples 1 and 3 in which the total area of the gas holes 144a is equal, the response time is further shorter and the water repellency value is smaller. Further, in Examples 1 to 8 in which the angle θ formed is in the range of 10 ° to 80 °, the response time is shorter and the water repellency value is smaller than those in Comparative Examples 3 to 7. In Comparative Examples 1 and 2 where θ is not in the range of 10 ° to 80 °, the response time is shorter than that in Comparative Example 3, but the value of water coverage is large.

  In comparison between Comparative Example 3 and Comparative Example 4, Comparative Example 3 in which the total area of the second outer gas holes 346a is larger than the total area of the first outer gas holes 344a is the second outer gas. The response time is shorter and the water coverage value is smaller than in Comparative Example 4 in which the total area of the holes 346a and the total area of the first outer gas holes 344a are equal. Therefore, even if the first outer gas hole and the second outer gas hole are not located at the corners as in the first to seventh embodiments, the total area of the second outer gas hole is the total of the first outer gas hole. It is considered that the effect of suppressing the adhesion of water to the sensor element and the effect of improving the responsiveness of gas concentration detection are obtained due to being larger than the area.

  Further, comparing Example 1 and Example 8, the gas passage hole is located at the boundary portion between the side surface and the bottom surface of the front end portion of the inner protective cover, and the gap between the outer opening surface of the gas passage hole and the bottom surface of the front end portion. In Example 8 in which the angle formed is 45 °, the value of water coverage is not changed and the response time is shortened.

[Evaluation Test 2]
For the gas concentration detection sensors of Example 2, Comparative Example 4 and Comparative Example 7, a vibration test was performed simulating the phenomenon that water accumulated in the piping due to vibration during operation gets wet on the sensor element. The state of the vibration test is shown in FIG. This vibration test was performed as follows. First, the gas concentration detection sensor was attached to the test chamber attached to the shaker at 45 ° from the vertical direction. In addition, a controller for controlling the heater output and a sensor output monitor for measuring the power control value of the heater were connected to the gas concentration detection sensor. Next, water was put into the test chamber, and the test chamber was vibrated with a sine wave while changing the frequency between 10 and 200 Hz with a vibrator. During vibration, the controller was controlled so that the heater in the sensor element was 100 ° C., and the power control value of the heater at this time was measured with a sensor output monitor. As the amount of water adhering to the sensor element increases, the temperature of the sensor element decreases, and the power control value increases to increase the output of the heater.

  The results of this evaluation test 2 are shown in FIG. As shown in FIG. 25, the power control value in Example 2 is smaller than that in Comparative Examples 4 and 7. From this, the gas concentration detection sensor of Example 2 has the first outer gas hole and the second outer gas hole formed so as to be located at the boundary portion between the side surface and the bottom surface of the outer protective cover. It was confirmed that the moisture content of the sensor element during vibration was smaller than in Comparative Examples 4 and 7 in which the outer gas holes were formed on the bottom surface.

[Evaluation Test 3]
About the gas concentration detection sensor of Example 8, Comparative Example 4, and Comparative Example 7, a water drain test was performed to confirm the state from the state in which water entered into the outer protective cover and the inner protective cover in advance until water was removed. . This test was performed using the broken water amount measuring device 950 shown in FIG. Specifically, first, the gas concentration detection sensor was attached to the pipe 970 while being inclined by 45 ° from the vertical direction. Then, the joint between the pipes 960 and 970 was made free of water, and instead, an arbitrary amount of water was injected into the outer protective cover and the inner protective cover of the gas concentration detection sensor in advance. In that state, the blower 980 was operated under a predetermined driving condition, and air was blown from the blower 980 to the pipe 960. During ventilation, the heater in the sensor element was controlled to 100 ° C., and the power control value of the heater at this time was measured. Note that if water is injected into the inner protective cover and water is attached to the sensor element, the temperature of the sensor element is lowered, so that the power control value is increased to increase the output of the heater. Therefore, the power control value becomes smaller as the water in the inner protective cover is removed by the air blowing.

  The results of this evaluation test 3 are shown in FIG. As can be seen from FIG. 26, there is no great difference in the power control value at the start of air blowing in both Example 8 and Comparative Examples 4 and 7. However, in Example 8, the power control value greatly decreases in 160 seconds after the air blowing starts. The value became stable after 160 seconds. On the other hand, in Comparative Example 4, the time until the power control value was stabilized was 200 seconds, and in Comparative Example 7, it was 600 seconds. From this, the gas concentration detection sensor of Example 8 was not only difficult for water to enter the protective cover and adhere to the sensor element compared to Comparative Examples 4 and 7, but also for example water entered the inner protective cover. However, it was confirmed that the water was easily drained (the water draining property was large). In the gas concentration detection sensor according to the eighth embodiment, the first outer gas hole 146a is located at the first corner 144b and the second outer gas hole 146a is located at the second corner 146b. It is considered that water easily escapes from the inner protective cover 130 because the gas passage hole 238a is located at the boundary between the side surface and the bottom surface of the inner protective cover 130. For example, as shown in FIG. 27, in the state where the gas concentration detection sensor of Example 8 is tilted by 45 °, the second outer gas hole 146a is located on the lowermost surface of the second gas chamber 126, and on the lowermost surface of the sensor element chamber 124. A gas passage hole 238a is located. Therefore, compared with Comparative Examples 4 and 7 in which the second outer gas hole 146a is not located at the second corner portion 146b, in Example 8, water in the second gas chamber 126 escapes from the second outer gas hole 146a. It is easy to make a water pool as shown in FIG. Similarly, compared with Comparative Examples 4 and 7 in which the gas passage hole 238a is not located at the boundary between the side surface and the bottom surface of the inner protective cover, the water in the inner protective cover 130 is discharged from the gas passage hole 238a in Example 8. It is easy to come off and it is difficult to form a water pool as shown in FIG. Although illustration is omitted, similarly, in the eighth embodiment, the water in the first gas chamber 122 is likely to escape from the first outer gas hole 144a in comparison with the fourth and seventh comparative examples, and it is difficult to collect the water. In addition, even if the angle at which the gas concentration detection sensor is tilted is other than 45 °, the gas concentration detection sensor of Example 8 is more water than Comparative Examples 4 and 7 if it is in the range of 0 ° to 90 °. The effect that it is easy to come off and it is hard to make a puddle is obtained. For example, in a cold region or winter, water may condense inside the protective cover of the gas concentration detection sensor attached to the exhaust path of the engine. When the engine is started in this state, water generated by condensation may adhere to the sensor element and cause cracks. Even in such a case, the gas concentration detection sensor of Example 8 is considered to be less susceptible to cracking than Comparative Examples 4 and 7 because water can easily escape.

  100, 300 Gas concentration detection sensor, 102 metal shell, 110 sensor element, 120, 320 protective cover, 122 first gas chamber, 124 sensor element chamber, 126 second gas chamber, 130, 330 inner protective cover, 132 large diameter portion 133 Step part, 134 First body part, 134a Inner gas hole, 134b Guide part, 135 Step part, 136 Second body part, 137 Step part, 138, 338 Tip part, 138a, 238a, 239a, 240a, 241a, 338a Gas passage hole, 239b Bottom surface, 138b Corner portion, 138c Bottom surface, 140, 340 Outer protective cover, 142 Large diameter portion, 144 Body portion, 144a, 344a First outer gas hole, 144b First corner portion, 144c Inner circumference Surface, 145 Stepped portion, 146 Tip portion, 146a, 346a Second outer side Hole, 146b second corner, 146c region, 200 piping, 400 gas concentration detection sensor, 402 metal shell, 420 protective cover, 422 upper chamber, 424 lower chamber, 430 first inner protective cover, 432 large diameter portion, 434 Tip part, 434a Gas passage hole, 434b Gas passage hole, 440 Second inner protective cover, 442 Large diameter part, 443 Step part, 443a Inner gas hole, 444 Body part, 446 Tip part, 446a Gas passage hole, 450 Outer protection Cover, 452 Large diameter portion, 454 tip portion, 454a Outer gas hole, 500 gas concentration detection sensor, 502 metal shell, 520 protective cover, 530 inner protective cover, 532 large diameter portion, 534 tip portion, 534a inner gas hole, 540 Outer protective cover, 542 Large diameter part, 544 Tip, 544a Gas passage 544b outer gas hole, 600 gas concentration detection sensor, 602 metal shell, 620 protective cover, 630 inner protective cover, 632 large diameter part, 634 tip, 634b guide part, 634c gas passage hole, 640 outer protective cover, 642 large Diameter portion, 644 tip portion, 644a outer gas hole, 644b inner peripheral surface, 700 gas concentration detection sensor, 720 protection cover, 730 inner protection cover, 738 tip portion, 740 outer protection cover, 738a gas passage hole, 744a first outer side Gas hole, 746a Second outer gas hole, 800 Gas concentration detection sensor, 802 Metal fitting, 820 Protective cover, 822 Upper chamber, 824 Lower chamber, 830 Inner protective cover, 832 Large diameter portion, 834 Tip, 834a Inner gas hole 834b Gas passage hole, 840 Intermediate protection Bar, 842 Large diameter portion, 843 Stepped portion, 843a First intermediate gas hole, 844 Body, 846 Tip portion, 846a Second intermediate gas hole, 850 Outer protective cover, 852 Large diameter portion, 854 Tip portion, 854a Outer gas Hole, 900 gas concentration detection sensor, 902 metal shell, 920 protective cover, 930 inner protective cover, 932 large diameter part, 934 tip part, 934a inner gas hole, 940 outer protective cover, 942 large diameter part, 944 tip part, 944a First outer gas hole, 944b Second outer gas hole, 950 Broken water amount measuring device, 960,970 pipe, 980 blower, 990 switching valve, 990a bypass.

Claims (6)

A sensor element capable of detecting a predetermined gas concentration of the gas to be measured;
A bottomed cylindrical inner protective cover covering the tip of the sensor element;
An outer protective cover having side and bottom surfaces;
A plurality of outer gas holes opened in a boundary portion between a side surface and a bottom surface of the outer protective cover;
An inner gas hole that allows the flow of the gas to be measured inside and outside the inner protective cover, and is located on the rear end side of the sensor element with respect to the outer gas hole;
With
Ri angle is 10 ° to 80 ° der the external opening surface and a bottom surface of the outer protective cover of the outer gas holes,
The outer protective cover includes a cylindrical body, a bottomed cylindrical tip having a smaller diameter than the body, and a step portion connecting the body and the tip. ,
The outer gas hole includes a plurality of first outer gas holes opened at a first corner that is a boundary portion between a side surface of a body portion of the outer protective cover and a bottom surface of a step portion of the outer protective cover, and the outer gas hole. A plurality of second outer gas holes opened in a second corner that is a boundary portion between the side surface and the bottom surface of the front end portion of the protective cover,
The inner gas hole is located on the rear end side of the sensor element from the first outer gas hole,
A first gas chamber surrounded by the body portion and the step portion of the outer protective cover and the inner protective cover, and communicated with the inside of the inner protective cover by the inner gas hole;
A second gas chamber surrounded by a front end portion of the outer protective cover and the inner protective cover and not in direct communication with the first gas chamber;
A gas passage hole that allows the flow of the gas to be measured between the second gas chamber and the inner side of the inner protective cover;
Gas concentration detection sensor equipped with . In the plurality of second outer gas holes, the total area of the openings is larger than the total area of the openings of the first outer gas holes.
The gas concentration detection sensor according to claim 1 . The gas passage hole is opened at a position other than the region on the extension of the second outer gas hole,
The gas concentration detection sensor according to claim 2 . Each of the plurality of first outer gas holes has the same area of the opening,
Each of the plurality of second outer gas holes has the same opening area,
The plurality of second outer gas holes have an opening area per one or more than the opening area per one of the first outer gas holes.
The gas concentration detection sensor according to claim 2 or 3 . The plurality of first outer gas holes are three or more holes located at equal intervals from each other,
The plurality of second outer gas holes are three or more holes located at equal intervals from each other.
The gas concentration detection sensor according to any one of claims 1 to 4 . The gas passage hole is opened at a boundary portion between a side surface and a bottom surface of the inner protective cover,
The angle formed between the outer opening surface of the gas passage hole and the bottom surface of the inner protective cover is 10 ° to 80 °.
The gas concentration detection sensor according to any one of claims 1 to 5 .